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Using cleaner fuels, such as hydrogen and developing more efficient combustion technologies are crucial in reducing NO x and N 2 O emissions, contributing to environmental concerns like air pollution and global warming. However, studies focusing on gas turbines using H 2 as fuel often overlook the emissions resulting from H 2 combustion. Given that gas turbines play a significant role in electricity generation globally, even minor improvements in their efficiency can lead to substantial cumulative benefits. Therefore, this study aims to address this gap by conducting a comprehensive environmental assessment using the life cycle assessment (LCA) methodology. By evaluating the environmental impacts of emissions from the combustion process of a conventional gas turbine and comparing them with potential emissions from H 2 combustion, this research seeks to provide valuable insights into the overall environmental performance of these technologies and contribute to sustainable energy development efforts. There have already been several LCA studies on H 2 production. In this study, we have identified the potential emissions and environmental impacts of H 2 combustion in gas turbines and compared them with the impact values of H 2 production regarding reference studies. The result shows that emissions during combustion should be considered in the identified life cycle impact categories. • Emissions released during hydrogen combustion are analyzed by gate to gate LCA. • AP values were found to be more sensitive to increasing NOx emission than EP and ODP. • GWP values due to N 2 O emission were determined as 0.72–1.11 E−4 kg CO 2 -eq. • Sensitivity analysis indicates that higher turbine efficiency reduces GWP. • This work highlights that emissions released during combustion are considerable. [ABSTRACT FROM AUTHOR]

In this study, the distribution of axial and radial velocities with the use of a PIV laser system was determined and the mixing power in a mixing tank with narrow and wide propeller impellers was measured. The pumping capacity and secondary circulation values in the mixing tank were calculated and on this basis, the energy efficiency of the operation of both types of propeller impellers was determined and compared with the efficiency of turbine impellers with inclined blades. It turned out that propeller impellers with wide blades are most effective as regards the amount of energy that should be supplied to the mixing tank to achieve the required mixing time. It was found that the share of pumping capacity in the total secondary circulation is almost twice as high as the share of induced circulation. Correlation equations for the dependence of the mixing power and dimensionless flow numbers on the pitch of the propeller blade were also formulated. All the results obtained were compared with the works of other authors. The paper also found that propeller impellers with a variable angle of inclination of the blade α depending on the current radius do not meet the theoretical assumption of a constant axial velocity of the liquid flowing out from of the impeller zone. For small radii of the impeller the explanation for this observation is the presence of the hub and shaft in the axis of the mixer and the effect of liquid slip for the steep agitator blades near the hub. For radii close to the radius of the stirrer, the reason is generation of induced circulation as the expense of the kinetic energy of the liquid flowing out of the impeller area. [ABSTRACT FROM AUTHOR]

Gas turbines efficiency growth is primarily associated with an increase in the operating temperature of the combustion chamber, which places new stringent requirements on the materials of thermal barrier coatings. Strontium cerate doped with tin SrCe 1- x Sn x O 3 where x = 0.1 ... 0.5, was proposed as a promising material. The research has shown that the lightly doped solid solution SrCe 1-x Sn x O 3 has an orthorhombic Pnma structure at x < 0.3, whereas at a high content of Sn4+ the monoclinic structure P2 1 /m becomes more favorable. Thermogravimetric analysis (TGA) in reducing atmosphere (5%H 2 in Ar) shows no mass lost as a result of unchangeable charge of Ce4+ and Sn4+. An increase in the distortion of the crystal lattice, due to the large difference in the ionic radii of Ce4+ and Sn4+, leads to a deterioration in the symmetry of the crystal lattice, a reduction of thermal conductivity (from 1.9 to 1.4 W m−1 K−1 at 1000 °C) and at the same time, growth of hardness and porosity. The increase in porosity, along with an increase in the required temperature of solid-state synthesis, indicates an enhancement in the melting point of the obtained materials. For the compounds with an orthorhombic structure, the thermal expansion coefficient increases with a growth in the Sn content, achieving a highest point 12.47·10−6 K−1 at 1100 °C for x = 0.3. The combination of the revealed properties and their comparison with advanced refractories makes the solid solution, primarily SrCe 0.5 Sn 0.5 O 3 , a promising material for application as thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Hydraulic turbines are increasingly used to regulate the electrical grid. They thus have to operate more often at off-design conditions where instabilities may develop leading to large pressure pulsations decreasing the life of the machines. In the present study, an adjustable guide vane system in the draft tube of a single regulated hydraulic turbine is developed. The aim is to mitigate the pressure pulsations when the turbine operates at part load operational regimes without significantly compromising the hydraulic efficiency of the turbine. The draft tube guide vane system, named DTGV, is composed of three guide vanes. Each guide vanes comprise two individual hydrofoils. The upper hydrofoil can rotate around an axis up to ±45°, and the lower is fixed. Therefore, the guide vanes are adjustable. The rotating vortex rope mitigation was investigated at two part-load operational regimes at a 12 m turbine head, a) Q/Q BEP = 0.59, and b) Q/Q BEP = 0.71. The results indicate that the DTGV system significantly mitigates the pressure pulsations, thereby improving the flexible operation of the turbine. The best mitigation outcome was for 0 GV configuration at both part-load operating conditions. The mitigation effects are better when the operating condition approaches BEP, and the rotating mode of the pressure pulsations tends to go towards the runner frequency (f/f 0 = 1). The hydraulic efficiency is found to be marginally affected by the guide vane system at part load operations and is improved at the best efficiency point (Q/Q BEP = 1) and high load Q/Q BEP = 1.21. [ABSTRACT FROM AUTHOR]

This study highlights the potential benefits of integrating Large Language Models (LLMs) into chemical engineering education. In this study, Chat-GPT, a user-friendly LLM, is used as a problem-solving tool. Chemical engineering education has traditionally focused on fundamental knowledge in the classroom with limited opportunities for hands-on problem-solving. To address this issue, our study proposes an LLMs-assisted problem-solving procedure. This approach promotes critical thinking, enhances problem-solving abilities, and facilitates a deeper understanding of core subjects. Furthermore, incorporating programming into chemical engineering education prepares students with vital Industry 4.0 skills for contemporary industrial practices. During our experimental lecture, we introduced a simple example of building a model to calculate steam turbine cycle efficiency, and assigned projects to students for exploring the possible use of LLMs in solving various aspect of chemical engineering problems. Although it received mixed feedback from students, it was found to be an accessible and practical tool for improving problem-solving efficiency. Analyzing the student projects, we identified five common difficulties and misconceptions and provided helpful suggestions for overcoming them. Our course has limitations regarding using advanced tools and addressing complex problems. We further provide two additional examples to better demonstrate how to integrate LLMs into core courses. We emphasize the importance of universities, professors, and students actively embracing and utilizing LLMs as tools for chemical engineering education. Students must develop critical thinking skills and a thorough understanding of the principles behind LLMs, taking responsibility for their use and creations. This study provides valuable insights for enhancing chemical engineering education's learning experience and outcomes by integrating LLMs. [Display omitted] • LLMs-assisted problem-solving procedure cultivate hands-on problem-solving and programming skills in ChemE education. • Student feedback on LLMs-assisted problem-solving procedure has been collected. • Suggestions to overcome misconceptions about integrating LLMs into ChemE education. • Provide examples and suggestions to aid integration of LLMs-assisted problem-solving procedure in ChemE education. • Recommendations for universities, ChemE professors, and students to adopt LLMs-assisted problem-solving procedure. [ABSTRACT FROM AUTHOR]

In this study, a multi-objective optimization design method was developed by combining, among other methods, single-phase flow analysis and the optimization method to simultaneously optimize the runner and collection device of an axial-flow hydraulic turbine with a collection device, using the power coefficient and axial thrust coefficient as objective functions. To verify the effectiveness of this design method, the characteristics of the optimized turbine were investigated through verification experiments and multiphase flow analysis, and were compared with the results of single-phase flow analysis. The results of single-phase flow analysis showed that the axial thrust coefficient of the optimized turbine was equivalent to that of the original turbine, while the power coefficient improved dramatically. However, the results of the multiphase flow analysis showed that although the axial thrust coefficient of the optimized turbine was increased compared to that of the original turbine, the power coefficient was significantly higher than that of the results in the single-phase flow analysis, due to a significant increase in the efficiency of the turbine, as well as an increase in the loading coefficient and the inlet velocity ratio, unlike the single-phase flow analysis. This indicates that this design method is effective in terms of output improvement. [ABSTRACT FROM AUTHOR]

To cooperate with new energy sources such as wind and solar, pumped storage units are required to frequently change conditions and operate under part loads, leading to the problem of violent pressure fluctuation and unit vibration. To meet this challenge, the next generation of pump-turbine runners will therefore have to be designed differently. The goal of this article is to construct a framework for broadening the operating range of pump-turbine to deep-part loads. In this study, a multi-objective optimization strategy for the runner with wider output range is suggested, wherein the blade control parameters, specifically the blade loading and blade lean angle, are optimized to enhance the efficiency, anti-cavitation, and stability of the pump-turbine runner. A runner with turbine output range of 40%–100% is optimized for a specific power station. Next, the impact of runner control parameters on runner performance is evaluated, and the runner geometric characteristics for different optimizing priorities such as the pump peak efficiency, cavitation performance, turbine rated efficiency, and turbine partial load efficiency, are concluded. The mutual restriction mechanism between the pump peak efficiency and cavitation performance of pump mode, as well as the turbine-rated efficiency and partial load efficiency of turbine mode, is revealed. The main contributions of this paper include putting forward an effective optimization design process for wide output pump-turbine, and pointing out the relationship between runner geometric characteristics and performance. The results indicate that the present approach can significantly improve the efficiency and stability of runners operating in deep-part loads. The blade loading pattern with hub section aft-loaded and shroud section fore-loaded, combined with negative blade lean angle, is recommended for such runners. Blades with a smaller wrap angle and lower arch are conducive to improving the pump peak efficiency and turbine-rated efficiency, while the opposite geometrical features are advantageous for improving the runner cavitation performance and efficiency performance under part load conditions. These findings can serve as an important guide for the development of runners with a wider output range. [ABSTRACT FROM AUTHOR]

Absorption cycles have been proposed not only for cooling but also for power generation, benefiting from temperature glide in heat exchangers, lowering exergy destruction. They can effectively utilise low-temperature solar, geothermal or waste heat. Apart from water-ammonia mixture, alternative working fluids may provide further advantages. Specifically attractive is an aqueous solution of salts such as lithium bromide (LiBr), also known from absorption cooling. Previous theoretical works found thermodynamic benefits of this concept mainly for heat sources around 100 °C and technical feasibility even for kW scale systems, but experimental works were limited. This work fills the gap by reporting on the world's first absorption power cycle (APC) using LiBr solution to convert low-temperature heat to power directly. A proof-of-concept system was built and operated with a 360 W design power output, featuring a nylon 3D printed turbine or measurement of temperature glide during phase change in the heat exchangers. This work includes extensive review of considerations for experimental system, design, commissioning and experimental performance. The measured turbine efficiency reached 25%, with a potential for significantly higher values. Over the range of explored conditions, if 65% expander performance was assumed, the maximal cycle efficiency could be around 5% and utilisation efficiency 0.5%. [Display omitted] • Comprehensively reviewed considerations for experimental LiBr absorption power cycle. • Experimental system designed, built and successfully operated. • Implemented plastic 3D printed turbine. • Measured temperature glide of desorber and absorber. • Cycle/utilisation efficiency up to 5%/0.5% with heat source/sink temperatures of about 88°/20 °C. [ABSTRACT FROM AUTHOR]

Hydroelectric power is a renewable and sustainable approach in energy production. However, hydro power generation is almost exclusively used at large scale (>10 kW). On a micro scale, it is still being assessed as a viable alternative to produce energy, even though this generation process seems to require lower installation and maintenance costs. The main aim of this work is the performance assessment of a micro hydro power station integrated into a rainwater harvesting system based on the optimal dimensioning of the turbine geometry. This project proposes different hydraulic heads for a sustainable model that uses the potential energy to generate electrical power in urban areas. As case of study, the system was set up for an industrial facility in the Toluca Metropolitan Zone, Mexico. A methodology was developed in order to: a) determine hydraulic setting-up based on the precipitation regime and operational requirements of the generator; b) assess an efficiency indicator under size variation of main geometric elements through Computational Fluid Dynamic (CFD); and c) validate the prototype throughout a 3D model. Due to the nature of the rainwater harvesting system, the type of the turbine selected was a Pelton turbine. Afterwards, hydraulic characteristics were defined, such as initial size of turbine, as well as the number and diameter of conduit pipes, nozzles, valves, and gates. Besides, the fluid behavior (velocity and pressure fields) in the turbine was analyzed by CFD to define a suitable geometry. Numerical modeling of the turbine allowed to estimate expected system efficiency according to the variation of a coefficient based on inlet and outlet velocities w 2 w 1. By means of an electronic circuit, which measured number of revolutions per minute and power generation (voltage and electrical current) of the system, efficiency and energy produced by the system were analyzed under both controlled conditions and real-time rainfall conditions. In general, the hydro power station managed to generate electrical energy using rainwater harvesting system which achieved up to 81.13% of efficiency. • A Pelton turbine is adapted within a rainwater harvesting system to produce electrical energy. • The design of turbine is based in two geometrical parameters: Length and height of the bucket. • Numerical modeling allowed to estimate turbine efficiency according to inlet and outlet velocities. • An efficiency of the system of up to 81.13 % is estimated simulating regimen of rainwater harvesting system. [ABSTRACT FROM AUTHOR]

Aiming at the high-efficiency OTEC application, a 30 kW radial-inflow turbine using ammonia was constructed via the one-dimensional design. In addition, a 3D CFD simulation was carried out to research the turbine performance. Furthermore, the effects of blade tip clearance on the flow characteristic in turbine were elucidated and the turbine performance under the off-design conditions was examined. It is indicated that the performance of the designed turbine is satisfactory with a theoretical isentropic efficiency of 85.2% under the design condition. The leakage flow encounters the scraping flow after leaving the tip clearance, forming the vortexes in the cross-section of the flow passage, which decreases the turbine efficiency, and the best ratio of blade tip clearance to inlet blade height is suggested to be 0.04–0.06. When the rotational speeds deviated from the design value, the vortexes appear in the flow passage of the turbine, resulting in non-negligible impact loss of blade and the consequent efficiency reduction. At the design rotational speed, the turbine shows a good adaptability to the inlet temperature variations with the inlet temperature varying from T 0 = 296K to T 0 = 304K. When the inlet pressure increases, the rotational speed corresponding to the maximum efficiency is also increased. [ABSTRACT FROM AUTHOR]

The wake effect, which is caused by the upstream turbines in a wind farm, adversely affects the efficiency of downstream turbines, leading to reduced energy generation and increased turbine fatigue loading. To mitigate this effect, a real-time wind farm control technique, i.e., wake redirection control (WRC), employing teaching learning-based optimization (TLBO) is introduced. This technique redirects the wakes away from the downstream turbines in real time, allowing them to generate more power by sacrificing some of the power generated by the upstream turbines. As a result, the total power generated by the wind farm is maximized. A low-fidelity 20-turbine real-life offshore wind farm is modeled and simulated in FLORISSE_M, the MATLAB version of the FLORIS (FLOw Redirection and Induction in Steady-state). The power produced by the wind farm model is maximized in real time by employing TLBO. The optimization results (i.e., the optimized yaw angles) are validated using the corresponding high-fidelity wind farm model developed in SOWFA (Simulator fOr Wind Farm Applications). Various results are presented to demonstrate that the TLBO-based WRC positively affects the power generated by the wind farm. • The power output of a model of a real-life offshore wind farm in South Korea is optimized. • Wake redirection control (WRC) based on Teaching Learning-based Optimization (TLBO) is proposed. • The proposed WRC is developed and applied in real time to the FLORIS model of the Korean wind farm. • The proposed WRC is validated using a high-fidelity model of the Korean wind farm in SOWFA. • Results demonstrate that the TLBO-based WRC could increase the overall wind farm power output. [ABSTRACT FROM AUTHOR]

This study examines the influence of turbine response type on the performance of a land-fixed Oscillating Water Column (OWC) under second-order Stokes waves of varying heights. Numerical modelling techniques, including the Finite Element Method, incompressible Reynolds-Averaged Navier–Stokes (RANS) equations with the Shear-Stress Transport (SST) k- ω turbulence model, and an Arbitrary Lagrangian–Eulerian (ALE) scheme, were employed to gain insights into OWC behaviour. The linear turbine consistently displayed reduced efficiency with increasing wave height, maintaining a stable peak non-dimensional wave number (k h). Conversely, the quadratic turbine exhibited peak efficiency within a narrower wave height range, strongly influenced by wave height. Non-dimensional volume flow rate, non-dimensional chamber pressure, chamber volume, and maximum force on the front wall remained unaffected by changes in wave height for the linear turbine. In contrast, the quadratic turbine was notably impacted by variations in wave height. Moreover, the quadratic turbine revealed stronger odd-numbered higher-order harmonic components in both force and pressure due to its non-linear response. Notably, both linear and quadratic response types exhibited sloshing at similar wave numbers, suggesting minimal influence of turbine response on sloshing behaviour. Finally, the derived non-dimensional turbine coefficients proved both turbines could scale OWC models with negligible scaling effects from the turbine. • The turbine choice (linear or quadratic) impacts OWC behaviour. • Linear turbines exhibit stability, less affected by wave height changes. • Quadratic turbines adapt to unpredictable waves but are strongly affected by wave height. • Quadratic turbines generate strong odd-numbered harmonics. • Scaling with non-dimensional coefficients shows minimal efficiency drop up to 10x. [ABSTRACT FROM AUTHOR]

Electric turbo compressor (ETC) can recover the exhaust energy and reduce the motor power consumption, which is the future development of the air management system for fuel cell. However, the large imbalances of axial thrust and energy between the compressor and turbine leads to low reliability and efficiency of ETC. In this study, a multi-objective optimization scheme was proposed to explore the lowest ETC axial thrust and electric power consumption. First, the coupled model including compressor, turbine and axial thrust sub-models were established in MATLAB. To verify the model, computational fluid dynamics(CFD) model were established in ANSYS CFX and experimental tests were carried out. The electric power differences between the MATLAB model and experiment is within 4.36 % and the axial thrust deviations between the MATLAB and CFD model is within 5.46 %.Then, eight geometric parameters of compressor and turbine rotors are selected as independent optimization variables. NSGA-ΙΙ multi-objective optimization algorithm was adopted to search for low axial thrust and power consumption solutions. Finally, the optimization results show that the efficiency of the compressor and turbine is increased by 6.39 % and 2.75 % at design point, respectively. The electric power consumed by the motor is reduced by 7.80 % and the axial thrust of the ETC is reduced by 18.83 %. • A novel multi-objective optimization scheme for electric turbo compressor is proposed. • A coupled model predicting the aerodynamic performance and axial thrust is developed. • CFD simulation and experimental tests are carried out to verify the coupled model. • NSGA-ΙΙ is used to seek for the optimal solution of motor power and axial thrust. • The electric power and axial thrust are reduced by 7.80 % and 18.83 %, respectively. [ABSTRACT FROM AUTHOR]

Variable-geometry turbines present significant improvements in both off-design cycle efficiency and enhanced engine responsiveness for future adaptive cycle engines. The adjustable vanes regulate the through-flow capacity by varying the installation angle and thus unavoidably require endwall clearance, resulting in profound implications for vane and downstream blade rows. Unsteady numerical simulations are carried out to investigate the vane-rotor flow interaction under the zero and partial clearance type of the adjustable vane in a 1.5-stage variable-geometry turbine. First, specific vortical structures and loss characteristics of upstream adjustable vane leakage flow at turning angles of −5°, 0°, and +5° are described. Then, the basic mechanisms of vane-rotor secondary flow interaction between acquired upstream leakage flow and downstream blade rows secondary flow is explored by the time-resolved method and quantitative detailed analysis method. The results show that adjustable vane vortex core area is the primary cause of internal loss within the vortex, and the mixing and interaction between the leakage vortex and other vortex systems contribute to secondary loss in the vane. Due to the downstream blade shear action caused by different flow velocity on the suction and pressure surfaces, the vane leakage flow fragments upon entering the R1 blade passage and develops downstream of the endwall region. Compared to the vane with zero clearance case at same turning angle, the intensity of the R1 tip leakage vortex at the design turning angle and open turning angle is reduced by 47.4 % and 23.66 % with the upstream partial clearance, respectively. The unsteady vane-rotor secondary flow interaction under different turning angles has large influence on the flow structure and loss characteristics of the downstream blade rows, and results in significant differences in the variation pattern and trend direction of the turbine performance. [Display omitted] • Vane-rotor interaction impacts endwall flow structures and turbine efficiency. • Adjustable vane leakage flow intensity varies with vane clearance and turning angles. • Partial clearance reduces downstream vortex intensity and secondary flow losses. • Vane turning angles control flow structures, potentially enhancing performance. • Unsteady effects crucial for evaluating variable-geometry turbine efficiency. [ABSTRACT FROM AUTHOR]

Enhancements in propulsion systems have played a key role in promoting aircraft fuel efficiency, which serves to achieve global decarbonization goals. In particular, investigation by decoupling individual components of the whole engine explicitly provides insight about improvement potential. In this study, stage-based exergetic assessments of the turbomachinery components such as compressor and turbine for a large turboprop engine used in military cargo aircraft are performed for five different flight cases. As a novelty, a new index called specific irreversibility ratio (SIR) showing irreversibility per unit power is established. In this regard, exergy efficiency of compressor changes from 86.6 % to 96.3 % throughout the 14 stages whereas for whole compressor, it is measured as 89.3 %. On the other hand, exergy efficiency of gas turbine changes from 92.5 % to 91.8 % throughout 2 stages whereas, for power turbine, it varies from 89.1 % to 89.7 % throughout 2 stages. Moreover, SIR of air compressor diminishes from 12.94 % to 4.26 % throughout 14 stages whereas those of gas turbine and power turbine increase from 8.17 % to 8.84 % and from 11.52 % to 12.58 % along with two stages, respectively. As for effect of flight cases, exergy efficiency of whole compressor changes by 2 % whereas those of gas and power turbines vary by 0.2 % and 0.5 %, respectively throughout flight cases. However, improvement potential rate of air compressor experiences a change between 23.81 kW and 58.19 kW whereas it varies between 27.31 kW and 50.74 kW for gas turbine and between 26.24 kW and 36.23 kW for power turbine. It could be inferred that variation of exergetic metrics throughout stages is more apparent in comparison with those of flight cases. The methodology improved in this study could help in understanding stage-based efficiency of turbomachinery components at on-design and off-design conditions. • Stage-based exergetic metrics for turboprop at dynamic flight. • Specific irreversibility ratio is showing irreversibility per unit power. • Stage-exergetic metrics is more apparent in comparison with flight phases. [ABSTRACT FROM AUTHOR]

The rational design of the turbine support structure ensures the safe operation of the system, achieves significant economic benefits and improves the efficiency of the turbine. This paper presents a novel turbine support structure capable of vertical movement along the guide column. In addition, the GA-FA-BP method has been developed for the optimization design of the support structure, which combines genetic algorithm (GA), firefly algorithm (FA) and back-propagation neural network (BP). The use of quadratic response surface (RS) method along with NSGA-II for the result validation of the GA-FA-BP model ensures the robustness and reliability of the optimization results. A finite element model is set up to analyse the mechanical behaviour of the support structure under 10 different combined load conditions. The most critical load conditions in the static mechanical models are used to generate training data, and the mass, deformation and equivalent stress of the optimized and unoptimized support structures are analyzed and compared. The results show that the optimized support structure can maintain deformation and equivalent stress within a weight reduction of 21.83% compared to the original design. Compared to a single optimization model, the proposed GA-FA-BP model shows higher accuracy with a correlation coefficient up to 0.9989. • Hybrid Machine Learning method (GA-FA-BP) combined ANN with GA and FA is proposed. • Optimal configuration of novel Hydro Turbine Support Structure is achieved. • Structural behaviors of Support Structure are analyzed in detail. • Effects of design parameters and their interactions are revealed deeply. • Rationality of design parameters and their interactions are revealed deeply. [ABSTRACT FROM AUTHOR]

• An innovative stand-alone C3MR LNG production combined with a power generation cycle. • Power generation system including Brayton cycle- Combined SCO2 Regeneration − ORC. • Energy, Exergy, Exergoeconomic, and Exergoenvironmental analysis based on Life Cycle Assessment. • Using machine learning for estimation of 4E objective function to reduce computation time. • The optimal solution is 45.14 % for ψ tot , 4.01 $/s for C ̇ total , 25.64 mPts/s for B ̇ total , and 153.16 kg/s for m ̇ LNG . This paper presents a novel self-contained liquefied natural gas (LNG) system for offshore natural gas extraction. The system combines a C3MR LNG process with mixed refrigerant and propane precooling cycles, integrated with a power generation system encompassing a gas cycle, supercritical carbon dioxide regeneration, and organic Rankine cycles. Utilizing Aspen Plus and the Peng-Robinson equation of state, the system is rigorously simulated. The study includes energetic, exergetic, exergoeconomic, and exergoenvironmental (4E) assessments, along with parametric studies to evaluate the influence of key parameters on objective functions. A genetic algorithm approach with four objective functions is employed to optimize system parameters. The exergoeconomic analysis shows that roughly 9% of the total cost rate associated with components refers to the power generation system, whereas 91% refers to the C3MR cycle. However, the exergoenvironmental analysis indicates that more than 57% of the total environmental impact rate associated with the components refers to the power generation system, while the remaining 43% refers to C3MR. The sensitivity analysis revealed the top five sensitive system parameters. Based on the multi-objective optimization, it was discussed that these parameters are: (a) hot inlet-cold outlet temperature difference of regenerator1 at 43 ° C , (b) air compressor isentropic efficiency at 90%, (c) MR compressors isentropic efficiency at 90%, (d) gas turbine isentropic efficiency at 90%, and (e) SCO2 turbine isentropic efficiency at 92%. Total ecergetic efficiency has the biggest share in the total improvement at 30.73%, followed by total environmental impact at 14.13%, total cost rate at 11.66% and LNG production rate at 0.57%. [ABSTRACT FROM AUTHOR]

The growing significance of renewable energy sources within the electricity market, along with the need to tap into lower head and capacity sites towards achieving recent sustainability goals, has highlighted the need for the development of hydro turbines and reversible machinery that exhibit enhanced performance across a broad operating envelope. This need is further compounded by the rising importance and strictness of environmental regulations, which necessitates the design of turbomachinery with improved environmental characteristics. In this context, Deriaz turbomachines emerge as a promising solution due to their numerous potential benefits. Notably, they can function as reversible pump-turbines, with remarkable hydraulic efficiency across a wide spectrum of operational loads. In this study, a numerical approach aimed at optimizing the design of a Deriaz turbine, in order to achieve high energy efficiency and improved fish-friendly behaviour in both pump and turbine operational modes, is introduced. Using a previously developed versatile design tool, coupled to numerical simulation and optimization tools, a new Deriaz reversible pump-turbine has been designed. Through a rigorous design process, numerous geometry variations have been analysed with the aim of improving the operational characteristics and environmental performance of the machine. The final geometry selected through the optimization procedure, was manufactured, and tested in both turbine and pump operating modes. By comparing the numerical to the experimental results, a remarkable agreement was observed particularly in turbine operation, thereby validating the design methodology and highlighting the efficacy of Deriaz turbines as a means to accomplish net-zero emissions goals. • A numerical approach for optimum design of mixed flow reversible turbines is introduced. • The new machine exhibits high energy efficiency and improved fish-friendly behaviour. • Fewer blades of optimal design can be a successful proposition for this machine type. • A scaled model was manufactured and tested in the Laboratory for both operation modes. • Numerical and experimental results agreement validates the new design methodology. [ABSTRACT FROM AUTHOR]

The rotating detonation gas turbine boasts several advantageous characteristics, including self-pressurization, minimal entropy increase, high thermal efficiency, and a high thrust-to-weight ratio. These features make it a promising candidate for the next generation of aerospace power devices. This study investigates the flow characteristics and performance attributes of the supersonic turbine stage coupled with a rotating detonation chamber based on different rotational speeds, blade ratio of rotor and stator, and hub radius, and uses DMD (Dynamic Mode Decomposition) to analyze the main modes of the supersonic turbine. The research identifies distinct wave modes in both the stator and rotor blades of the supersonic turbine. In the stator blades, the modes include waveless contact modes, opposite side λ -wave oblique shock wave modes, and derived modes from opposite side λ -wave oblique shock waves. In the rotor blades, the modes encompass non-separation modes (waveless modes, asymmetric dual λ -wave modes, oblique cut wave modes, and single-side λ -wave modes on the pressure surface), leading-edge stator excitation single separation bubble modes, saddle-type separation modes, and dual separation bubble modes. The efficiency and power of the supersonic turbine stage increase with the rotational speed. The turbine efficiency is highest when the blade ratio is 10:7. Under multi-wave mode conditions, detonation waves demonstrate adaptive self-regulation abilities, ultimately achieving equilibrium in speed, detonation wave height, and spacing. The dominant modes in the stator blades and combustion chamber are governed by detonation waves and slip lines, while in rotor blades, the primary mode is the flow-directional vortex mode governed by detonation waves and slip lines at a frequency lower than their propagation frequency. This research holds certain reference significance for understanding the internal flow characteristics of rotating detonation gas turbines, as well as discussing the patterns of efficiency, power, and load characteristics, thereby offering valuable insights for the practical application of rotating detonation gas turbines. • Supersonic turbine stage with different parameters coupled with RDC. • DMD mode characteristics of supersonic turbine coupled with RDC. • Unsteady modes of wave system of interaction between TGVs and combustion chamber. • Unsteady modes of shock wave system of turbine rotor blade. • Performance characteristics of supersonic turbine stage under different parameter conditions. [ABSTRACT FROM AUTHOR]

• RDC passage area has a significant impact on operating range of rotating detonation gas turbine. • The increase of RDC passage area makes the operating range of gas turbine move to the higher power. • Equivalence ratio of RDC replaces turbine efficiency as the greatest influence factor on cycle efficiency increment with different combustor passage areas. • Qualitative analysis based on sensitivity analysis of component parameters is further optimized to announced the comprehensive reason for change of cycle efficiency increment. Application of rotating detonation combustion can significantly enhance gas turbine performance, but the limited flow capacity caused by normally aspirated characteristic of rotating detonation combustor (RDC) severely constrains the operating range of gas turbine. In this paper, the detailed investigation was carried out for the influence of RDC passage area on cycle characteristic parameters for a 25MW single shaft gas turbine. The results demonstrated that changes of RDC passage area had a significant impact on operating range of rotating detonation gas turbine. As RDC passage area increased, operating range of gas turbine moved to the higher power, with the slight increases for cycle efficiency, cycle efficiency increment and net power increment compared to traditional gas turbine at identical net power. For the process when RDC passage area decreased from 0.0272 m2 to 0.0240 m2, the lower working limit of rotating detonation gas turbine decreased to 53.3 % of rated power, in which equivalence ratio of RDC replaced turbine efficiency as the greatest influence factor on cycle efficiency increment. [ABSTRACT FROM AUTHOR]

• CO 2 emission characteristic of thermal power units for peak shaving is modeled. • The carbon reduction rate considering renewable power accommodation is defined. • A low-carbon scheduling method based on carbon reduction rate is proposed. • Impact of renewable power on CO 2 emissions of power systems is studied with a case. To accommodate the high penetration of renewable power, the operational flexibility of thermal power units is highly required by the power system, so thermal power units frequently operate under peak shaving conditions. The CO 2 emission characteristics of a thermal power unit are significantly influenced by the load factor, and also by the installed capacity and design parameters of the thermal power unit. Therefore, detailed CO 2 emission characteristics of thermal power units should be modeled and considered in the low-carbon scheduling of the power system. In this study, thermal power units are classified by live steam parameters, installed capacities, reheat stages, cooling modes, and operation modes, and the models of detailed CO 2 emission characteristics are developed and validated. The turbine isentropic efficiency, boiler thermal efficiency, and auxiliary power consumption are comprehensively considered in the CO 2 emission model. A new indicator is defined to evaluate the reduction of carbon emissions in a power system when a TPU accommodates per unit of renewable power generation, and an optimization method for low-carbon scheduling based on it is proposed. Finally, a reference case study is conducted. Results show that the total carbon emissions for a day of the proposed low-carbon scheduling method are 0.06 %−0.20 % less than the efficiency priority method, and 1.53 %−2.36 % less than the capacity weighting method. [ABSTRACT FROM AUTHOR]

The Indian River, which is celebrated for its breathtaking beauty and diverse heritage of cultures, has an extensive amount of potential for producing green hydroelectric electricity. 7.5 % of the world's energy came from renewable sources in 2022, with India making up 36 % of the share and growing. India has nearly reached the 5 GW objective for small hydro projects and has reached 68 % of its 175 GW renewable energy ambition. At 90 % efficiency, bulb turbines are hydroelectric turbines that produce power from water, making them a perfect choice for high flow rates and low water head conditions. In order to optimize bulb turbines, this research investigates the use of computational fluid dynamics (CFD) to assess variables including the number of guiding vanes, the angle of the draft tube, and the design of the blades. According to studies, efficiency is increased when guiding vanes increase. The geometry of guiding vanes also has a significant impact on performance. Draft tubes, which restore kinetic energy from water entering the turbine, can enhance efficiency with proper design. Adding anti-cavitation capabilities to runner blades improves performance even further. CFD models verify these conclusions, with little variations from the field data. By fine-tuning important parameters such as 14 guiding vanes and adjusting the draft tube angle to 2.5°, the turbine's efficiency jumped from 87 % to 97 %. [ABSTRACT FROM AUTHOR]

• Thermodynamic cycle with isothermal expansion. • Isothermal nozzles: theory and design. • Simulation and experimental studies on nozzles with isothermal expansion. • Innovative gas isothermal turbine: design, simulation calculations and experimental studies. The efficiency of power plants with steam or gas turbines depends on the efficiencies of a thermodynamic cycle and devices implementing this cycle. In the case of high power outputs, we cannot expect a significant increase in the efficiency of individual devices. Therefore, what remains is to increase the efficiency of the implemented thermodynamic cycle − the complex Rankine cycle in the case of steam turbines or the extended Brayton cycle in gas turbine units. The efficiencies of these cycles depend on the hot reservoir temperatures, limited by the materials used. The solution seems to be the thermodynamic cycles with the highest efficiency within given temperature limits, the „generalized Carnot cycles". About gas turbines, such a cycle is the Ericsson cycle. The most difficult element of this cycle is carrying out high-temperature expansion. So far, there is no literature data on a technical device implementing this process. In this article, we present a method for designing turbine nozzles for isothermal expansion and the results of experimental tests of the first isothermal turbine. In the case of gas microturbines with a regenerator, isothermal expansion can increase efficiency from 24% to 28% up to 36%. An increase in efficiency of several to a dozen percentage points is expected for Organic Rankine Cycle (ORC) turbines. Due to such significant increases in energy generation efficiency, an isothermal turbine may become a future solution for energy systems. [ABSTRACT FROM AUTHOR]

• Fourteen parameters, which represented all the aerofoil's vane shape of a micro-scale turbine, i.e., 2–12 kW, were accurately studied. • Their influence on both the vane performance, stage operation, and the overall cycle's performance is determined. • The Linear Point Advanced Side 2 showed almost no influence on the turbine performance. • The Trailing Edge Wedge Angle and Trailing Edge Beta Angle were the most influential parameters. • This results in enhancing the stator and the turbine efficiency by around 11% and 5%, respectively, compared to the baseline design. The ever-elevating importance of turbines makes enhancing their performance a crucial point. In most cases, the required performance can be achieved by improving the turbine's components, i.e., its rotary part, stationary part, and volute. However, this requires a lot of effort, especially when dealing with rotary parts that are time-consuming and costly because of the rotor. Having said that, most of the previous studies have improved turbomachinery by using the latter method. The current study, on the other hand, highlights the importance of only one component, the cheaper one, as a key factor. So, once the numerical modelling was validated using a previous experimental published work, fourteen parameters, which represented all the aerofoil's vane shape (the stationary part of the turbine only) of a micro-scale turbine i.e. 2–12 kW, were accurately studied with the aim of highlighting their influence on both the vane performance, stage operation, and the overall cycle's performance as well. The results showed that while parameter 14 i.e. Linear Point Advanced Side 2 showed almost no influence and parameters 5 and 6 i.e. Trailing Edge Wedge Angle and Trailing Edge Beta Angle were the most influential ones, all the other parameters showed a significant effect on the overall turbines' performance, especially at higher PR values. Moreover, the results have also confirmed that the best values of the mentioned parameters are 0.33 mm, 17 Deg., −25 Deg., 41 Deg., 1 Deg., 55 Deg., 0.3 mm, 0 Deg., 19 mm, 31 mm, 77 mm and 0 mm for all thirteen parameters, respectively. This results in enhancing the stator and the turbine efficiency by around 11 % and 5 % respectively, compared to the baseline design. [ABSTRACT FROM AUTHOR]

In light of the extended exposure of tidal stream energy generation systems to seawater, which can lead to marine biofouling and subsequent reductions in turbine efficiency, this paper presents a deep learning-based method for the identification of pollutant adhesion. This method aims to rapidly assess the status of turbine pollutant adhesion in tidal energy generation systems. A dataset of adhesion images from tidal stream energy generation system under varying levels of pollution was obtained through underwater experiments with artificial fouling. Three different deep learning algorithms were employed to investigate the enhancement of underwater biofouling image quality. Image segmentation algorithms were used to extract and identify information related to the location and area of biofouling. The results demonstrate that the proposed deep learning-based pollutant adhesion identification method effectively recognizes the adhesion status on turbine blades, improving the accuracy of pollutant identification. This approach provides an efficient and accurate means of pollutant adhesion detection and management for the operation and maintenance of tidal stream energy generation systems, ultimately reducing operational costs. • A deep learning-based method for pollutant adhesion recognition is proposed. • The prototypes of the turbine component for the tidal energy generator device are designed, manufactured and tested under water. • Underwater images of the biofouling status of underwater tidal energy turbine devices are collected. • The recognition method can effectively improve the accuracy of identification of pollutant adhesion. [ABSTRACT FROM AUTHOR]

The thermodynamic analysis of a geothermal-based integrated energy system to produce liquid hydrogen, cooling, hot water, and power was presented in this study. The investigated system consists geothermal subsystems, a modified organic Rankine cycle (ORC), a PEM electrolyzer, and a liquid hydrogen storage source. Different organic fluids including refrigerants R113, R123, and R134a were investigated to increase the system performance. Analysis of organic fluids showed that the best organic fluid is R123 because it helps to increase the performance of the system. The authors employed the Design-Expert software and RSM for optimum results purposes, and the objective functions were chosen to be exergy efficiency (EE) and cost rate (CR). Following introduction of design variables, the mass flow rate of input to the evaporator, the temperature of input to heat recovery vapor generator, turbine efficiency, turbine input temperature, evaporator pinch point temperature, and pump efficiency, their impact on the system's performance were investigated. The optimal values for EE and CR were ultimately found to be 43.91 % and 45.12 $/h, respectively. Also, in this research, seven regions within Canada were investigated for the launch of the proposed system. The studied cities were Victoria, Vancouver, Regina, St. John's, Dawson Creek, Whitehorse, and Port Alberni. Finally, Regina was chosen because of the system's superior performance in electricity production at a reasonable cost in that area. The environmental results showed that the presented energy system in Regina city could help to expand 5 ha of green space by producing electricity at the rate of 4993.03 MWh in one year. The findings indicated that implementing the suggested system in Regina would help prevent 1018.6 tons of CO 2 /MWh from being emitted into the environment yearly, only by chipping in 24445.9 $/ton of CO 2 per year. • Thermodynamic analysis of a multiple energy production system. • Geothermal energy for commissioning in Canada. • Optimization by response surface method (RSM). • The optimal values for EE and CR were ultimately found to be 43.91 % and 45.12 $/h. [ABSTRACT FROM AUTHOR]

Hydraulic short circuit (HSC), corresponding to the simultaneous operation of the pumps and turbines, enhances the power flexibility of a pumped storage power plant (PSPP). However, comprehensive analyses are imperative to guarantee a secure and reliable operation within this novel operational mode. Unforeseen engaging dynamics may perturb the safe operation of the groups. The existing literature still lacks comprehensive analysis concerning the water flow structures and tubomachines performances during HSC operations across the entire hydraulic circuit. This paper evaluates the fluid-dynamic interactions between the units during HSC operations using 3D unsteady-state CFD simulations of an existing PSPP not designed for enduring such conditions. The total pressure evolution in the upstream trifurcation and consequent effects on the turbine performance are discussed by the selected HSC configurations. In the trifurcation, between the pumping unit and the turbine, the relative head loss reaches 1,78% and, eventually, anomalies of the velocity field are documented on a case-by-case basis. Moreover, the pump operations are investigated in HSC operations with the matter of efficiency detriments, cavitation and air entrainment risk. The results highlight that the pumping unit in HSC compared to the baseline operation undergoes a reduction in hydraulic efficiency up to 0.51% due to the operation of adjacent turbine. The documented observations led to the application of additional criteria for the safe and stable governing control of the PSPP in HSC. • CFD research assesses HSC impacts on penstock trifurcation and turbomachine performance. • In HSC, flow perturbations from trifurcations can reduce turbine efficiency by 0.55%. • Pumps in HSC may lose hydraulic efficiency due to nearby turbine operations. • Pump cavitation and air entrainment risk are investigated during HSC service. • Preferable configurations of pump and turbines for HSC operations are identified. [ABSTRACT FROM AUTHOR]

Vertical-axis wind turbines (VAWT) are excellent candidates to complement traditional wind turbines and increase the total wind energy capacity. Development of VAWT has been hampered by their low efficiency and structural unreliability, which are related to the occurrence of dynamic stall. Dynamic stall consists of the formation, growth, and shedding of large-scale vortices, followed by massive flow separation. The vortex shedding is detrimental to the turbine's efficiency and causes significant load fluctuations that jeopardise the turbine's structural integrity. We present a comprehensive experimental characterisation of dynamic stall on a VAWT blade including time-resolved load and velocity field measurements. Particular attention is dedicated to the dilemma faced by VAWT to either operate at lower tip-speed ratios to maximise their peak aerodynamic performance but experience dynamic stall, or to avoid dynamic stall at the cost of reducing their peak performance. Based on the results, we map turbine operating conditions to one of three regimes: deep stall, light stall, and no stall. The light stall regime offers VAWT the best compromise in the dynamic stall dilemma as it yields positive tangential forces during the upwind and downwind rotation and reduces load transients by 75% compared to the deep stall regime. [ABSTRACT FROM AUTHOR]

One of the most promising technologies for sea-wave energy conversion is the one based on the OWC principle. In a system of this type, the oscillatory motion of the sea waves is converted into a bi-directional air flow which is commonly exploited by means of a self-rectifying turbine such as the Wells turbine, the simplest and most reliable device for this purpose. The vast majority of experiments on Wells turbines and OWC devices has analyzed their performance from a global point of view, often in experimental facilities where the turbine was operated under stationary flow conditions. This paper presents the results of the experimental investigation carried out on a Wells turbine, by measuring the flow field both upstream and downstream of the rotor, in a laboratory set-up capable to reproduce the bi-directional airflow typical of an OWC system. The investigation aims to evaluate the local performance of the Wells turbine under unsteady flow conditions. The experimental measurements allow the identification of the loss components that affect the performance of the turbine. Viscous losses, due to the aerodynamic of the rotor cascade, represent the main contribution to the total losses, and appear larger than kinetic energy losses at the machine exhaust. • Measurements of the local performance of a Wells turbine under bi-directional flow. • Loss components and turbine efficiency are calculated. • Most of losses are due to the aerodynamic behavior of the rotor. • Non-stationary operating conditions strongly affect the performance of the turbine. • Rotor solidity at the hub and tip leakage are main responsible of turbine losses. [ABSTRACT FROM AUTHOR]

The growing demand for high efficiency in gas turbines requires elevated turbine inlet temperatures, underscoring the critical necessity of implementing high-efficiency film cooling technology on the turbine endwall. However, the traditional cooling layout encounters challenges in the under-cooled areas on the turbine endwall. Therefore, a partitioned film cooling layout with shaped holes on the endwall was proposed based on the heat transfer and flow characteristics of the endwall and the cooling properties of the shaped holes. Based on the heat transfer coefficient distribution on the endwall surface, the endwall was divided into four regions, arranged with different shaped holes for cooling. Numerical and experimental methods were used to study the aerodynamic and cooling characteristics of the partitioned cooling layout. The results indicated that the partitioned cooling layout's cooling performance was significantly improved compared with that of the conventional film hole arrangement. Additionally, it was verified that adjusting the compound angle of the shaped holes further provided a uniform film coverage. More importantly, by adjusting the mass flow of the coolant, the optimized blowing ratios of different regions on the partitioned film cooling layout were explored. The optimized blowing ratio scheme significantly enhanced the film cooling effectiveness due to the varying sensitivity of different shaped holes to the blowing ratio. The results of this work hold significance for advancing film cooling effectiveness and turbine performance. [ABSTRACT FROM AUTHOR]

• High specific speed Francis turbine as an alternative to low specific speed Kaplan/semi-Kaplan/Propeller turbine. • Comprehensive experimental studies of the high specific speed Francis turbine. • Multi-aspect experimental approach to determining the Thoma cavitation number. • Comprehensive vortex visualization for various cavitation states in the draft tube. • Saddles were found on the performance characteristics for high guide vane opening angles. The paper presents comprehensive experimental research on a high specific speed model Francis turbine with a characteristic runner diameter of 250 mm under the head of 12 m. Essentially, the turbine was designed for use at heads between 10 and 50 m, which are typical for installations with low specific speed Kaplan turbines. The basic performance, cavitation and runaway characteristics of the machine, which were determined as a result of the work, are quite rarely available in the literature in the case of high specific speed Francis turbines. The turbine achieved the maximum efficiency of 91%, kinematic specific speed of 82, and relatively wide operation range, so that it can be attractive as an alternative to the low specific speed Kaplan, semi-Kaplan or propeller turbines. In result of the basic laboratory tests, the performance characteristics of the machine operation in a wide range of guide vane opening angles between 9° and 36° as well as the shell efficiency characteristics were determined. On the characteristics plotted vs. rotational speed, the saddle effect was identified for the guide vane opening angles with values greater than the optimal one (22°). During the operation of the machine in the area of saddles, the change in the flow rate took quite surprising patterns. The share of the turbine thrust torque in the total torque was also determined, the characteristics of which are also burdened with a similar saddle effect. In the case of cavitation tests, a multi-aspect approach to cavitation diagnostics was used to characterize the cavitation phenomenon from the viewpoint of various criteria. Following this approach, the signals of the draft tube wall acceleration, acoustic emission at the draft tube cone upper flange, and pressure fluctuations inside the draft tube were used. The determined cavitation characteristics indicate little cavitation susceptibility of the Francis turbine blade system, despite the presented turbine having been designed to operate at higher flow rates than the classic high head Francis turbines with long interblade channels. The cavitating flow in the draft tube, directly below the runner, was also visualized during the cavitation tests. The paper presents the results of visualization for all cavitation states at five selected settings of the guide vane opening angle (two states in Partial Load, two states in High Load area and one state in the Best Efficiency Point), thanks to which it was possible to track the development of vortices during pressure reduction in the flow system. The runaway coefficient was determined as a result of the runaway tests. The value of 1.497 was reached at the optimum guide vane opening angle. Additionally, the work also presents in detail the efficiency scale effects to be expected at prototype turbines, i.e. those intended for operation at a higher head and with larger runner diameters. The efficiency of the machine with a runner diameter of 1.5 m and working at a head of 50 m reaches ∼93%. The influence of water viscosity on the change in efficiency of the prototype turbine is also shown. The presented methodology can be used for the proper selection of turbines intended for hydropower plants and for the proper installation of the runner in respect to the tailwater level in order to avoid the phenomenon of cavitation erosion. [ABSTRACT FROM AUTHOR]

An enormous amount of the world's electricity is produced by steam power plants. The existence of a liquid phase in the steam turbine results in an efficiency drop and mechanical losses, which are very expensive due to its high price. Creating a suction slot in the stationary blade of the steam turbine for sucking the supercooled vapor and wetness fraction in the low-pressure stages of the turbine is one of the most effective methods of preserving the rotor blades against corrosion and erosion. The Eulerian-Eulerian method is employed for modeling the condensing flow. In the current research, the impact of the suction slot location and number on the surfaces of the turbine blades is investigated on condensation, total suction ratio, liquid suction ratio, average droplet radius, and condensation losses. Optimization is performed by the TOPSIS algorithm. Based on the results, the location and number of the suction slots affect the flow pattern in the turbine blade. Creating a suction slot in the optimal case has a total suction ratio of 4.1 %, which decreases the liquid suction ratio, condensation losses, and average droplet radius, respectively, by 5.28 %, 6 %, and 25 % compared to the original case. • Supercooled vapor suction in steam turbine is studied to control wetness parameters. • Effect of slot on steam turbine is investigated for supercooled vapor suction. • Optimization by TOPSIS is employed to find the optimal slot location and number. • Suction slot from the suction side has a greater influence than the pressure side. • Optimal mode is caused reduction in the droplet radius and condensation losses. [ABSTRACT FROM AUTHOR]

The pre-swirl system, a vital system responsible for supplying cooling gas to the turbine blades. However, the pre-swirl system involves rotor-stator matching and intricate power-heat conversion challenges, which has led to a bottleneck in the development of its temperature drop potential. This study investigates the traditional pre-swirl system structure to identify factors limiting its temperature drop performance. A novel design idea is proposed to enhance the temperature drop performance by reducing the power consumption in the pre-swirl system. Subsequently, the structure optimization and performance improvement for pre-swirl system are conducted through the design of four vane-shaped receiver hole models. To assess the effectiveness of these enhancements, the thermodynamic and aerodynamic characteristics of the pre-swirl system before and after optimizations are evaluated using numerical simulations. Finally, the system temperature drop characteristics equipped with optimal receiver holes are thoroughly evaluated by experimental test analysis. The findings reveal that the new type of pre-swirl system, featuring a leading-edge vane-shaped receiver hole design and the removal of the cover-plate cavity, surpasses traditional designs. It exhibits a remarkable 35.3 % improvement in the receiver hole discharge coefficient, a 39.7 % reduction in system entropy increase, and a 6.36 kW/(kg/s) decrease in specific power consumption. Significantly, experimental verification demonstrates a 10 % increase in the nozzle pressure ratio, the temperature drop of pre-swirl system increased by 53.6 % from 23.5K to 36.1K, and the temperature drop efficiency of pre-swirl system increased from 0.567 to 0.872. Therefore, this study offers valuable insights for the design of high-performance pre-swirl systems, contributing to the overall improvement of turbine efficiency. [Display omitted] • The leading-edge vane-shaped receiver holes can improve pre-swirl system performance. • New pre-swirl system has temperature drop significantly improved by 53.6 %. • New pre-swirl system has entropy increase reduced by 39.7 %. • New pre-swirl system has specific power consumption reduced by 6.36 kW/(kg/s). • New pre-swirl system has the temperature drop efficiency is 0.872. [ABSTRACT FROM AUTHOR]

This study aims to optimize a multi-energy production system that utilizes sustainable geothermal energy as its primary power source. The system comprises several subsystems, including a geothermal well, an organic rankine cycle (ORC) unit, an absorption chiller, and a proton exchange membrane (PEM) electrolyzer. The study examined the impact of variations in seven key parameters, including turbine inlet temperature, evaporator pinch point temperature, pump inlet temperature, evaporator inlet temperature, evaporator inlet mass flow rate, turbine efficiency, and pump efficiency, on the overall system performance. The Response Surface Methodology (RSM) was employed to find the optimum point of the system. To facilitate the practical implementation of the system, the research team assessed its viability in 10 different Iranian cities, all known for their substantial geothermal energy potential. Among the cities, Zahedan emerged as the most suitable location for deploying the system, given its robust energy production potential. The results showed that January, with a production of 626.4 MW h of electricity, and November, with a production of 622.8 MWh of electricity, are the best months for the system to operate in Zahedan city. The environmental aspect of the system also yielded noteworthy results. By setting up the proposed system in Zahedan city, it is possible to prevent the emission of 1472.411 tons of carbon dioxide by producing 7217.7 MWh of electricity throughout the year at a cost of 35337.86 $. Additionally, the proposed system can help expand 7 ha of green space, providing the electricity needed by 2349 people throughout the year. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of very low head (VLH) axial turbines in rivers and canals is one of the new methods of utilizing hydropower on a small scale. These types of turbines are environmentally friendly and, due to the lack of need for a dam, penstock, spiral casing, and draft tube, have low construction costs. Higher efficiency and improved turbine performance also lead to lower overall costs. In this study, the primary objective is to pinpoint the key factors that affect the VLH turbine performance and optimize it accordingly. The design variables encompass various elements, including leading and trailing edge angles, maximum thickness across three blade sections, tip clearance, outlet angles of guide vanes, and the count of guide vanes and runner blades. In this regard, during the optimization phase, only the most influential factors as ascertained through sensitivity analysis are considered. Subsequently, employing surrogate modeling, an evolutionary optimization algorithm is applied to identify the optimal configuration of design variables. Critical design variables were identified, including the blade angles in the middle section, the trailing edge angles, the outlet angle of the guide vanes, and the number of runner blades. Following the optimization process, the optimal turbine exhibited notable improvements, with a 2.26 % increase in efficiency and a remarkable 10.4 % boost in power output compared to the original configuration. Moreover, the optimized turbine showcased improved performance beyond the design point, with approximately a 2 % efficiency increase across all discharge rates. [ABSTRACT FROM AUTHOR]

Pumped storage represents an economically viable, highly efficient, and extensive energy storage solution, receiving substantial research attention worldwide. This study utilized the energy dissipation of fish swimming in the water, and the traveling wave plate was arranged in a vertical rectangular flow channel to obtain energy through reverse thinking. Numerical simulation was employed to investigate the performance characteristics of the traveling wave turbine under varying wave number across high and low water head. The results reveal that the efficiency at low water head starts to increase and then decreases with the increase of wave number. There is an optimal wave number N = 4 to maximize turbine efficiency, and the maximum efficiency under low water head condition is 89.35 %. The efficiency of the high head condition shows a continuous upward trend, with a maximum value of 92.27 % in the range of wave number studied. With the increase of wave number, the instantaneous mass flow coefficient and power coefficient become more stable. The advantage of increasing the wave number is that more traveling wave plates can participate in energy capture, which is conducive to reducing the force required by each traveling wave plate and making the pressure distribution in each working cavity more regular. [ABSTRACT FROM AUTHOR]

• Numerical analysis optimizes hydrokinetic turbine design and performance parameters. • The study explores five novel turbine geometries with varying blade configurations. • The flow field around the blade profiles was studied at different angular positions. • Two-blade turbine configuration achieves maximum torque and power coefficient. Hydrokinetic turbines harness the kinetic energy of flowing water to generate sustainable power, offering a promising avenue for clean and renewable energy. An effective turbine design is necessary for optimizing power extraction even in scenarios with minimal head. Among the various hydrokinetic turbine designs, the Savonius hydrokinetic turbine holds prominence. Over the past century, numerous studies have aimed to refine the design of the Savonius rotor, yet there remains no consensus on the ideal configuration for these turbines. Addressing this, the current study introduces a novel approach with detailed 3D transient simulations to enhance the water turbine performance via blade modifications, transitioning from traditional analyses that primarily focus on wind turbines. This research develops and analyzes five unique turbine geometries, each varying in blade number, diameter, and angular positions. A detailed numerical analysis was conducted using the sliding mesh technique to assess their impact on turbine efficiency and output, using an inlet water velocity of 0.5 m/s and a tip speed ratio ranging from 0.7 to 1.3. Findings indicate that a two-blade turbine configuration achieves the highest torque coefficient of 0.295, which is 2.41 times higher than that of a four-bladed design with equal blade diameter at a tip speed ratio of 0.7. It also reaches a maximum power coefficient of 0.217, marking a 155 % increase over four-bladed designs with equal blade diameter at a tip speed ratio of 0.9. [ABSTRACT FROM AUTHOR]

The lead-cooled fast reactor (LFR) engenders novel requisites for the energy conversion system when applied to maritime ships and distributed energy supply systems. The supercritical carbon dioxide (sCO 2) Brayton cycle, with the advantages of high efficiency, space-saving, simplicity, and flexibility, is a promising candidate for LFR. Here, we present the first study on the off-design operation of the sCO 2 cycle for LFR, with the turbine and compressor arranged on a single shaft (coaxial-shaft) or two shafts (split-shaft). The off-design performances of the system are investigated using four rotational speed (RS) control-based hybrid control strategies. We showed that the split-shaft system controlled by separate turbine speed and compressor speed has a wider operating space of power load than the coaxial-shaft system. Among the four investigated control strategies, the RS-inventory hybrid control can achieve the best thermal efficiency during load variation by operating at the turbine speed and mass flow rate corresponding to the optimal turbine isentropic efficiency. The maximum operating space of power load (0%–100 %) can be achieved by the RS-turbine inlet pressure hybrid control and the RS-bypass hybrid control. Our study can provide guidance for the flexible and safe part-load operation for small-scale modular Gen-IV nuclear reactors. • Off-design performance of sCO 2 cycle for LFR is evaluated. • Arrangements of turbomachines in coaxial- and split-shaft are compared. • Four hybrid control strategies based on the rotational speed control are studied. • Operating space of thermal efficiency and power load are analyzed. [ABSTRACT FROM AUTHOR]

• A novel inverted cross-flow turbine and its design method for the low and ultra-low head hydraulic condition were proposed. • The four-step parametric studies were conducted to achieve the optimized turbine design. • The turbine achieved higher than 60 % efficiency range in the ultra-low head condition (under 3 m water head) by using a simple spiral nozzle and without a guide vane. • The optimized turbine maximum efficiency was achieved 72.92 % efficiency at the turbine speed 170 RPM with 8.01 m of water head. This study aimed to address the challenges of micro-hydropower generation in low-head environments to expand the proportion of hydropower in renewable energy and achieve a carbon neutrality policy. To achieve these goals, various factors affecting the micro-hydro systems, including geographical constraints, construction costs, and grid connectivity, were reviewed and assessed. The results concluded that a novel type of cross-flow turbine with inverted structures, improved the economic feasibility, productivity, and installability of micro-hydropower plants by reducing head losses in open channels or small streams. The parametric studies consisted of four steps: first, designing the initial inverted cross-flow turbine based on the traditional design rules; for the second and third steps, a parametric study for comparing the runner diameter ratio and the number of blades is conducted; and in the last step optimized turbine was designed. The best efficiency point of the optimized inverted cross-flow turbine was 72.92 % at a runner rotational speed of 170 RPM with a 0.75 runner diameter ratio and 35 blades. The optimized turbine was improved by 7.8 % in power and 7.35 % in efficiency, higher than the initial turbine. From the hill chart comparison between the initial and optimized turbine, operation range expansion was confirmed. Overall, this research demonstrates the potential of the inverted cross-flow turbine under low-head conditions. [ABSTRACT FROM AUTHOR]

Compressible flow turbines usually work under choked conditions, requiring an analysis for the performance estimation. The Mean-line modeling is a fast and accurate method extensively used for the analysis and design purposes. However, it has not already been well-investigated for axial flow turbines specially in choked conditions. The present study investigates the issue from three novel aspects. First, a detailed study is accomplished on the inconsistencies of Mean-line method respect to the physics of real flows. It is discussed that the conditions related to maximum mass flow rate through a nozzle and the Mach number one at the throat are different. In fact, the latter condition is not quite physical. Second, a complete algorithm is utilized to implement the aforementioned considerations for the analysis of turbines. This algorithm includes an innovative Blade Solution Algorithm (BSA) and Turbine Solution Algorithm (TSA). The BSA solves the blade rows of turbine using the basic laws of Physics and real-gas properties. In the TSA, a robust and efficient procedure is presented so the solution of turbine converges in wide ranges of boundary conditions with minimum iterations. The results demonstrate that the algorithm generate close maps to the previous studies. Eventually in the third part, since a fast and robust Mean-line algorithm is crucial in optimization, the code is utilized for a design based on optimization using the Genetic Algorithm. In this procedure, all geometrical parameters are optimized as decision parameters rather than the use of old and approximate correlations. This is done along with novel constraints, which not only maximizes efficiency, but also puts the output power, mass flow rate and turbine size in appropriate ranges. The optimization results in a 3.5% rise in efficiency. • Two efficient and real-time approaches are proposed for Mean-line analysis of axial-flow turbines. • All the procedures are based on the real-gas models. • The performance of turbines can be estimated under a wide range of working conditions, including choked conditions. • Optimization is accomplished on an experimental turbine using the Genetic Algorithm, resulting in an almost 3.5% rise in efficiency. • The impact of various parameters on the turbine efficiency are discussed. [ABSTRACT FROM AUTHOR]

• An improved GANormaly model for fast and accurate diagnosis of blade attachment in marine current turbines is proposed. • The method is based on unsupervised learning, eliminating the need for human tagging and improving the efficiency of human capital use. • Deblurring recovery of underwater images to improve the efficiency of turbine blade attachment cleaning. • Enables fast and accurate diagnosis of blade adhesion on marine current turbines, promoting clean energy production and the development of marine current power generation technology. Marine current energy is a clean and renewable resource that is an available energy source with future power generation potential. However, complex subsea conditions can cause blade failures in marine current turbines (MCTs); therefore, the fault diagnosis of MCTs is essential to ensure their good operation. Image-based diagnosis is a nondestructive approach. To improve the efficiency of using human capital, this study uses the unsupervised learning network GANomaly trained only with normal samples to diagnose the leaf attachment of MCTs. Marine biofouling is a lengthy process, and according to the literature, the blades were contaminated by a 1.1-mm-thick layer of lithium lubricating grease, therefore, this study uses ropes to simulate this attachment. First, we address the problem of blurred underwater images collected using a multiscale retinex enhancement algorithm with color recovery to form a new dataset. GANomaly is modified to diagnose MCT blades with different attachment degrees. The experimental results show that the accuracy of the enhanced dataset is improved by 1.75 %, and the accuracy of the improved GANomaly model reaches 91.23 %, thereby enhancing the efficiency of the fault diagnosis of MCTs. [ABSTRACT FROM AUTHOR]

Improving the efficiency of turbines for power plants and aircraft engines is an increasingly important research subject. Ternary Mo-Si-B alloys, consisting of a molybdenum solid solution (Mo ss) phase and two intermetallic phases Mo 5 SiB 2 (T2) and Mo 3 Si, are able to combine balanced room temperature fracture toughness, high temperature creep strength and good oxidation performance. However, the high density (typically > 9 g/cm3) of this class of alloys is a drawback when used as structural materials for rotating components. In this study, high potential Mo-V-Si-B materials which provide a reduced density by about 17 % as compared with the reference alloy Mo-9Si-8B were investigated. A comparative characterization was carried out on sintered (FAST) and arc-melted Mo-40V-9Si-8B alloys. Compressive creep tests reveal competitive creep resistance of this new type of alloys in the application relevant temperature regime. • Powder metallurgical and arc-melted Mo-40V-9Si-8B alloys showed either (Mo,V) ss or silicide matrix phase, respectively. • FIB tomography shows that the (Mo,V) ss and the (Mo,V) 5 SiB 2 phase are continuous and interpenetrating. • The creep response of the PM alloys was mainly governed by the Mo ss phase shown by KAM images of the crept microstructure. • In case of heat-treated FAST Mo-40V-9Si-8B, a grain coarsening from 0.5 μm to 3 μm resulted in a decrease of creep rates. • The creep performance of PM Mo-Si-B alloys, can be competitive against Nickel-based superalloy CMSX-4. [ABSTRACT FROM AUTHOR]

This paper focuses on the determination of the optimal operating scenario of an Externally-Fired Micro-Gas turbine utilizing syngas produced by biomass gasification. Biomass exploitation can contribute to the achievement of the net-zero emissions target in 2050. This can be boosted by the advancement of externally-fired technology. In this study, a dual-objective optimization process, including a validated thermodynamic model, is combined with preliminary cost insights to assist the decision-making process. The resulting performance is compared with the actual data-based performance of a reference natural-gas-fired Micro-Gas Turbine. The performance comparison is performed through an exergetic analysis, identifying the main losses contributors. The optimization results in an externally-fired performance of 77.9 kW el electrical power and 20.3% efficiency, improved by 31.5% compared to the average current externally-fired demonstrated efficiencies. Yet, there is still room for improvement to reach natural-gas-fired Micro-Gas Turbine efficiency. The study highlights an unavoidable efficiency decrease of at least 4.0 percentage points due to the use of syngas itself instead of natural gas, which conversely increases heat recovery potential. However, compared to the state-of-the-art demonstrations, the proposed analysis is a significant step towards efficiency improvement, which can be exploited for future biomass demonstrations, attractive for electricity generation as well. • Performance of an externally-fired microturbine using biomass syngas is optimized. • Design point is determined through an optimization with preliminary cost insights. • Performance is compared with the validated data from a natural gas microturbine. • Electrical efficiency improved by 31.5% compared to average current demonstrations. • Syngas use results in an unavoidable efficiency decrease of 4.0 percentage points. [ABSTRACT FROM AUTHOR]

The dual-pressure organic Rankine cycle (DPORC) system can obtain a better temperature match between the heat source and working fluid due to the existence of two evaporation processes, which can significantly improve the utilization rate of the heat source and reduce the irreversible loss. Firstly, single-objective optimization of the DPORC system is conducted based on the orthogonal design method with thermal efficiency, exergy efficiency, electricity production cost (EPC) and annual emission reduction (AER) as the performance indicators, respectively. Then, multi-objective optimization of all performance indicators is carried out based on the comprehensive scoring method. Finally, the contribution rates of the operation parameters and the optimal working conditions under different external conditions are investigated. The results show that condensation temperature, high-pressure evaporation temperature and turbine isentropic efficiency are the most critical parameters for system comprehensive performance. When heat source temperature is 170 °C, thermal efficiency, exergy efficiency, EPC and AER under the optimal working conditions are 11.91%, 48.46%, 2.71 × 10−2$/kWh and 11.17 × 105kg, respectively. With the increase of heat source temperature, condensation temperature and turbine isentropic efficiency always have an important influence on system comprehensive performance. The contribution rates of high-pressure evaporation temperature and low-pressure evaporation temperature increase and decrease, respectively. Better comprehensive performance can be obtained by using HC working fluid. • Multi-objective optimization of the DPORC system is conducted by the orthogonal design method. • The effect of operation parameters on system performance is comprehensively investigated. • The effect of external conditions on the contribution rates of the parameters and the optimal working conditions is analyzed. • Condensation temperature, HP evaporation temperature and turbine isentropic efficiency are the most critical parameters. • Better comprehensive performance can be obtained by using HC working fluid. [ABSTRACT FROM AUTHOR]

From the point of view of performance and economical in power plants, it is necessary to pay attention to the measurement of wet steam. The objective of this research is to employ the multi-objective black-box technique to minimize thermodynamic losses related to wet losses and improve the efficiency of the steam turbine, disregarding the process of film water deposition on the blade surface. For this purpose, a complete model of the steam turbine stage consisting of a stator-rotor is used to study wet steam. The simultaneous effects of two design variables on the performance of the steam turbine stage have been analyzed. The numerical model of wet steam flow has been used for calculating the values of the optimization criteria, including integral of wetness fraction (IWF), integral of mean droplet radius (IDR), turbine stage efficiency (TSE), condensation loss rate (L r), and mass flow rate (M r). According to the results, the temperature and pressure ratio were suggested to be 339.44 (K) and 0.51 (−), respectively, which improved the IWF by 30% and the IDR by about 7.3%. Also, the optimal mode increased TSE by about 1.3% and led to the reduction of L r and M r , by about 29%, and 1.3%, respectively. • Multi-objective black-box optimization (GA) is implemented for steam turbine stage. • Two-dimensional stator-rotor blade-to-blade channels have been studied numerically. • Two MATLAB and Fluent software are coupled together for optimization simultaneously. • Inlet stagnation temperature and pressure ratio are design variables in optimization. • IWF, IDR, TSE, L r , and M r are the optimized design criteria in the stage outlet. [ABSTRACT FROM AUTHOR]

As one of the most promising methods for harnessing ocean wave energy, the oscillating water column device has been intensively investigated, especially the Wells turbine within the device. However, owing to the low efficiency of the Wells turbine, it is essential to provide a deep insight into the loss audit and loss quantification. The scope of this work is to explore the main loss mechanisms due to the irreversibility. The aerodynamic losses and associated flow behaviors within four typical working conditions were quantified and analyzed in detail based on entropy generation and exergy analysis. The loss weight of the Wells turbine indicates that the secondary flow loss coupled with the friction loss is the largest, 34%, under the stall condition. The blade tip streamlines show that a large-scale vortex structure on the blade suction caused by the interaction of the leakage flow and the suction side flow is one of the main reasons of the decreasing blade loading and growth of low-energy fluids. Moreover, the exergy loss gradually increases with the increasing angle of attack, leading to a dramatic drop of the second law efficiency from 0.52 at the maximum torque point to 0.22 at the stall condition. [ABSTRACT FROM AUTHOR]

The gravitational water vortex hydraulic turbine is an appropriate turbine to be used under from a small to medium water flow rate and at a low head. This turbine extracts energy from an induced vortex in a basin, using a coaxial rotor with a vertical axis. The gravitational turbine has efficiencies that vary between 17 and 85%. Increasing the circulation was required in order to achieve the highest efficiency. The circulation is a function of some geometric parameters of the turbine, such as the ratios between the basin diameter (D) and the outlet diameter (d), d / D ; the basin height (H) and D , H / D ; the inlet channel width (w) and D , w / D ; the inlet channel height (h) and D , h / D ; the inlet channel long (L) and D , L / D ; and the wrap-around angle (γ). Response surface methodology was utilized to determine the optimal geometry that results in the highest circulation. The values of the six variables that give the highest circulation of 2.089 m2/s were d / D = 0.167, H / D = 1.840, w / D = 0.2, h / D = 0.599, L / D = 0.500 and γ = 179.976°. In addition, an exponential equation was proposed for calculating the inlet velocity for each treatment. This equation is a function of d / D and the coefficient of discharge, C d. The results of the exponential function were compared with experimental data from other investigations. [Display omitted] • GWVHT is a turbine suitable to use in low head and small to medium water flow rates. • GWVHT is optimized through the response surface methodology. • Transition-state, VoF, and k- ε RNG model were chosen to perform the CFD analyses. • The highest circulation obtained was 2.089 m2/s. [ABSTRACT FROM AUTHOR]

In this study, we created an optimization design method for axial flow runner by combining one-dimensional design method with a design of experiments, a response surface method, and an optimization method. This design method was applied to the runner of a palm-sized ultra-small axial flow hydraulic turbine, which can be applied to existing pipelines and low head of an open channel. We investigated the mechanism of performance improvement by examining turbine performance and internal flow of the obtained runner with numerical analysis and experiments and by surveying vortex structure and loss. As a result, the optimized runner designed with the design method in this study presented about 9.1% of significant improvement in the experimental value of turbine efficiency compared to the original runner designed only with the one-dimensional design method. This was because the optimized runner experienced less loss by tip leakage vortex and vortex near the hub of the runner outlet on the runner, especially less loss of vortex by swirling flow downstream from the runner. The results showed the effectiveness of the design method in this study. [ABSTRACT FROM AUTHOR]

Ocean Thermal Energy Conversion (OTEC), as a new type of renewable energy, has huge development potential. Turbine is the most critical component in the ocean thermal energy conversion system, which directly determines the performance and energy conversion efficiency of the system. Therefore, the optimal design of turbines is very important to improve the efficiency of ocean thermal energy conversion. Based on the full consideration of the small temperature difference application characteristics of ocean thermal energy conversion and the special thermophysical properties of organic working fluids, this paper designs an ammonia working centripetal turbine with a power of 100 kW for OTEC applications, and then analyzes the effect of different geometric parameters on turbine performance. At the same time, the key parameters of the turbine are optimized based on full three-dimensional CFD numerical simulation analysis. It's shown that the nozzle blade installation angle has a very important impact on the performance of the turbine. Through optimization, when the nozzle blade installation angle reaches 30.5°, the efficiency is 91.77%, which is 6.25% points higher than the design value. The internal flow field performance is the best without obvious shock wave and reverse vortex phenomenon, which further improves the efficiency of the turbine and improves the internal flow. [ABSTRACT FROM AUTHOR]